1. Field of the Invention
The invention relates to computer numerical control (CNC) of spectacle lens machining.
2. Relevant Art
Despite far-reaching automation, known CNC spectacle lens machining apparatuses, in particular spectacle lens edging machines, require a CNC-controlled particular accuracy, and therefore skill, for example in inserting into the apparatus a lens blank to be machined, and/or are demanding and complicated to operate as regards inputting the parameters required for the spectacle lens machining, which are a function of the optometric data of the spectacle wearer, the selected spectacle frame, the spectacle lens material and the like.
In the known CNC spectacle lens machining apparatuses, it stills happens that a finally machined spectacle lens cannot be inserted into the selected spectacle frame, and therefore has to be remachined.
The problem on which the invention is based is to create a method for machining spectacle lenses by means of a CNC spectacle lens edging machine, by means of which the operation of the CNC spectacle lens machining apparatus is simplified and made easier, and by means of which an increased accuracy is achieved for the shaped spectacle lens.
Furthermore, the invention is based on the problem of improving a CNC spectacle lens machining apparatus such that operation is substantially simplified in conjunction with increased machining accuracy.
Starting from this formation of the problem, a method is disclosed for machining spectacle lenses by means of a CNC spectacle lens machining apparatus which comprises, according to the invention, the steps of:
inputting the optometric data of the spectacle wearer, that is to say dioptric number, values and angles of a cylindrical or prismatic cut, intensity and position of a reading portion, into a computer which cooperates with a control device of the apparatus,
inputting the eye""s viewing point or interpupilary distance (PD values) of the spectacle wearer into the computer by means of a selected spectacle frame,
inputting the shape data of a selected spectacle frame, if appropriate of the profile, the shape and the circumference of a bevel groove of the spectacle frame or of a spectacle lens groove or a spectacle lens dubbed corner, corresponding to the spectacle frame, into the computer,
inputting the spectacle lens material, that is to say silicate glass or plastic such as CR39 or polycarbonate, into the computer,
calculating the required lens blank diameter in the computer and displaying the lens blank diameter,
inserting a lens blank of the desired diameter into the apparatus,
if appropriate, checking the position of the lens blank inserted into the apparatus, and incorporating the position of the lens blank by calculation in the machining data,
if appropriate, calculating the profile of a bevel, a groove or a dubbed corner on the shaped spectacle lens from at least one of the following parameters: optometric data, PD values, shape data, radii of the front surface and rear surface and the center thickness of the spectacle lens,
if appropriate, comparing the shape of the bevel groove in the selected spectacle frame with the shape of the bevel groove in a spectacle lens edging tool in the machine, and deciding by computation whether the machining of the bevel is or is not possible without or with taking account of correction values by computer,
CNC machining of the lens blank, which comprises at least shaping the spectacle lens and, if appropriate, also machining a bevel, a spectacle lens groove or a spectacle lens dubbed corner, if appropriate also machining the optical surface(s), it being advantageous that it is possible for correction values to be incorporated by calculation into the machining data before the CNC machining of the lens blank as a function of prescribed machining tolerances, workpiece tolerances and tool tolerances and detected deviations thereof.
In addition to these steps, there can be performed on a screen a monitoring display of the input values and of the required lens blank diameter, and a positionally accurate imaging of the lens blank and, superimposed thereon, of the shape of the spectacle lens, such that all the parameters required for the spectacle lens machining can be checked visually.
When the bevel groove in the spectacle frame and the bevel resulting from the bevel groove in the spectacle lens edging tool are imaged and assigned on the circumference of the spectacle lens on a screen, it is further possible for the feasibility of the bevel machining to be checked visually.
In order to relieve the operator from particular attentiveness and care when inputting the parameters, inputting the dats required for spectacle lens machining can preferably be performed in machine-readable form, the required data can be stored at least partially on at least one data medium such as a magnetic strip card, bar code card or a floppy disk.
Again, the PD values need not be input alphanumerically into a keyboard when the PD values are determined by an automatic video recording system and the data determined are led directly into the computer of the control device. If the shape data of a selected spectacle frame are not available stored on a data medium, the shape data of a selected spectacle frame, including the bevel profile, the bevel shape and the circumference, can be determined in a contactless fashion in a scanning device and led directly to the computer.
When the dimensions and the shape of the bevel groove in the spectacle lens edging tool are determined in a preferably contactless fashion by a video recording system or laser scanner system, and these data are led directly to the computer, it is possible to use the computer to establish whether a bevel can be produced on a spectacle lens, which is to be shaped, in accordance with the dimensions and the shape of the bevel groove in the selected spectacle frame with the aid of the existing spectacle lens edging tool as a function of the wear of the bevel groove in the spectacle lens edging tool, if appropriate with incorporation of a correction value by calculation.
In order to calculate the bevel profile on the circumference of a spectacle lens which is to be shaped, either it is possible for the profile of the front edge and the rear edge of a spectacle lens, which is to be shaped, to be scanned in the apparatus, preferably in a contactless fashion by means of a video recording system, whereupon the data are led directly to the computer, which calculates therefrom the profile of a bevel suitable for the selected spectacle frame and uses these values to control the bevel machining; or the profile of the front edge and of the rear edge of a spectacle lens corresponding to a selected spectacle frame are calculated by the computer using at lease one of the parameters of: optometric data, PD values, shape data, radii of the front surface and rear surface and the center thickness, which calculates therefrom the profile of a bevel suitable for the selected spectacle frame and uses these data to control the bevel machining, the profile of the front edge and of the rear edge can preferably be calculated from the radii of the front surface and rear surface along with the center thickness, and/or can be taken over from a computer for the surface machining. This computer for surface machining can be the same computer as for the edge machining.
The input and calculated data can be conveyed to a spectacle lens manufacturer as order data for the lens blank by long-distance data transmission, such that after the ordered lens blank has arrived, it is possible to perform the final machining of the lens blank in a spectacle lens machining apparatus attached to the computer.
It is also possible for the input and calculated data to be conveyed to a spectacle lens manufacturer as order data for a finally machined spectacle lens by means of long-distance data transmission, such that after the arrival of the finally machined spectacle lens all that is required is for the optician to insert the spectacle lenses into a selected spectacle frame.
All the calculations for determining the machining data can be performed by a host computer which, as an external control unit, controls a plurality of machines and units in multitasking mode.
The solution of the problem mentioned at the beginning is also served by a spectacle lens machining apparatus, having a housing, a machining chamber in the housing, a spectacle lens holding shaft and a machining device in the chamber, a computer connected to a control device for controlling the machining of a lens blank, held by the spectacle lens holding shaft, by means of the machining device, an input keyboard connected to the computer, and a data reading device, which can be connected to the control device, for data for the spectacle lens machining which are stored on a data medium card, such as a magnetic strip card, bar code card or the like.
Moreover, it is possible for there to be present a floppy disk drive, connected to the computer, for data, stored on a floppy disk, for the spectacle lens machining, and/or a scanning device, connected to the computer, for the spectacle lens opening in a selected spectacle frame as well as for the profile, the cross-sectional shape and the circumference of a bevel groove in the spectacle frame, and/or a sensor, connected to the computer, for detecting characterizing markings on a lens blank, on packaging for a lens blank or a storage container for lens blanks and/or on a spectacle frame, packaging for a spectacle frame or on a storage container for a spectacle frame, and/or a video recording system, which can be connected to the control device, for automatically recording the PD values of the spectacle wearer with reference to a selected spectacle frame, and/or a vertex retractionmeter, connected to the computer, for automatically recording the optical values of a shaped spectacle lens or a lens blank, and/or a device, connected to the computer, for mounting a block or sucker on a lens blank or a shaped spectacle lens, and for automatically transmitting the position of the block or sucker on the lens blank or the shaped spectacle lens to the computer, the result being that it is superfluous for an operator to make alphanumeric inputs into the apparatus.
No particular requirements are made of the accuracy with which the lens blank is inserted into the spectacle lens holding shaft when a detection device, connected to the computer, is present for the position of a lens to be machined with reference to the spectacle lens holding shaft, since the position of the lens blank detected by the detection device with reference to the spectacle lens holding shaft can be taken into account computationally when machining the lens blank.
It is likewise possible to provide a detection device, connected to the computer, for the diameter of a lens blank, held in the spectacle lens holding shaft and/or for the profile of the front edge and the rear edge of the circumference of a shaped spectacle lens, the data of which can be used by the computer to calculate the bevel profile on the circumference of the shaped spectacle lens and to control the machining thereof.
When, furthermore, a detection device, connected to the computer, for the shape and the dimensions of a bevel groove in a spectacle lens edging tool is present, the bevel groove in the spectacle lens edging tool can be compared with the bevel groove in the selected frame, and a decision can be made as to whether or not a spectacle lens with the calculated bevel can be inserted into the selected spectacle frame, if appropriate with incorporation of correction values by calculation as a function of the shape and the dimensions of the bevel groove in the selected spectacle frame and in the spectacle lens edging tool.
The detection devices for the position of a lens which is to be machined with reference to the spectacle lens holding shaft, for the diameter of a lens blank held in the spectacle lens holding shaft and/or for the profile of the front edge and the rear edge of the circumference of a shaped spectacle lens, and the detection device for the shape and the dimensions of a bevel groove in a spectacle lens edging tool can preferably comprise a charge coupled device or CCD camera or a laser scanner system, it being possible for the detection device for the diameter of a lens blank held in the spectacle lens holding shaft and/or for the profile of the front edge and the rear edge of the circumference of a shaped spectacle lens, and the detection device for the shape and the dimensions of a bevel groove in a spectacle lens edging tool, to be implemented as separate devices or in a fashion combined from a single device.
A screen, connected to the computer, for displaying the input date and/or for imaging the lens blank with the required diameter and/or the spectacle lens, which is aligned in the correct position with reference to the lens blank and is to be shaped, and/or the bevel groove cross section of a selected spectacle frame, as well as the bevel, resulting from the dimensions and the shape of the bevel groove of the spectacle lens edging tool, of a spectacle lens to be shaped facilitates the visual monitoring by the operator with regard to the data which have been input or read in, and with regard to the finished spectacle lens, but is not mandatory for the automatic running of the spectacle lens machining.
When all inputs are performed by means of automatic data reading units or scanning devices in the way outlined above, the spectacle lens edging machine according to the invention need have only a very simple input keyboard, which comprises only a switch-on key, a start key, an interruption key for the running machining operation, a stop key and, if appropriate, a key for controlling an aftercut.